NullSecurity Croatia has reported on Facebook and Twitter that it claimed responsibility for the release of the footage and advised the Office of the Chief State Prosecutor (DORH) to improve the protection of its server.

The video recording was posted on November 27 by the user named RemetinecLIVE. The timecode on the footage shows that the recording was edited from the original running time of about 50 minutes to 12 minutes and six seconds.

The footage was removed on Thursday evening, but it reappeared on YouTube this morning.

Upon the posting of the video recording, the Croatian state prosecutorial authorities said last night they would demand a prompt investigation in order to establish who did it and thus revealed classified information. This offence carries a prison term from three months to three years.

DORH also called on the media to remove the video recording from their web portals, otherwise they breach laws on confidentiality.

The Croatian Journalists' Association head, Zdenko Duka, told press this was an attempt of media censorship, explaining that it was not prosecutors but the courts that could ban the publication of confidential material.

Asked whether the police had made some steps in this regard, Interior Ministry spokesman Krunoslav Borovec said they were still waiting for an order to be sent from the prosecutorial authorities.

DORH said it would issue a new statement on the matter.

The posting of the footage of Sanader's testimony which he gave in the Remetinec detention centre was condemned by his lawyers and the lawyer for the Croatian Democratic Union (HDZ), Vladimir Gredelj.

The group of hackers have also announced publication of material which they say will "shake" the Croatian public, the HDZ and the Croatian Prime Minister and HDZ leader Jadranka Kosor.